Метод вибору мережі доступу в мобільній системі SDR при вертикальному хендовері

Abstract

Запропоновано метод вибору мережі призначення процедури вертикального хендоверу в гетерогенних мобільних радіосистемах зі здатністю реконфігуруватися, побудованих на основі технології Software Defined Radio: сформульовано задачу вибору мережі та представлено процедуру вертикального хендоверу в таких системах. Змодельовано і проаналізовано процес розв’язання оптимізаційної задачі прийняття рішення про вертикальний хендовер за допомогою системи Mathcad. In order to satisfy emerging user requirements in advanced services/applications, provided seamlessly, operators have to deploy complex network topologies of heterogeneous nature, where different Radio Access Technologies (RATs) co-exist in single composite network with shared resources. Network operator will have assign the appropriate RAT to perform the respective task, so as to achieve the required quality of service, cost-effectively. In such circumstances, there is a need in vertical handover – mechanism of transferring current connections from one radio access network to another. Furthermore, reconfigurable (adjustable) depending on the telecommunication environment devices should be used as user terminals. Software Defined Radio (SDR) technology has been identified as a key enabler of such equipment and networks. This paper is devoted to the vertical handover problem solving. Vertical handover decision problem is very important, because it has strong influence on the network performance and the quality of service of nodes. There are two main aspects of this problem: how to define “best” and how to determine the best access bearer. In the article the access selection method of vertical handover process in heterogeneous reconfigurable mobile radio systems based on SDR technology is proposed: access selection problem is formulated and vertical handover algorithm in such systems is described. To perform an accurate decision the proposed decision process rely on multiple attributes decision-making, while providing a small delay due to the sequential filtration and reduction of the set of possible alternatives. The method allows optimizing network and radio resources utilization and quality of service in heterogeneous network and also provides dynamic adaptation of the access selection decisionmaking rules according to the different telecommunication conditions and network policies. The proposed selection criteria, on the one hand, is simple and well-formalized, and therefore does not require significant computational and time costs, but on the other – provides adaptability. Vertical handover algorithm takes into account peculiarities of SDR devices and therefore can be used in SDR networks. To evaluate the method Mathcad system was used. The effectiveness of the method is confirmed by simulation example for UMTS, GPRS and WLAN networks, which is based on proposed decision-making process where decision is made not on the basis of the absolute advantage of alternative but on the basis of difference between the current and alternative modes parameters, therefore minimizing the amount of intersystem handovers causing additional load on the system. Simulation confirmed that linear aggregation function in multiple attributes decision-making process is the most appropriate because it provides almost the same results as the other methods but in a much simpler way.